1. Field of the Invention
This invention is directed to an improved process wherein aniline is synthesized from phenol over ammonia.
2. Description of the Prior Art
Aniline is an important organic chemical. Many highly useful products can be produced from it. Aniline is the simplest of the primary aromatic amines. Aniline and other aromatic amines can be prepared by several prior art methods, one, for example, is the reduction of nitro compounds obtained by direct nitration of the benzene ring. Important derivatives of aniline include toluidines, xylidenes, n-alkyl, n-aryl and n-acyl derivatives.
Aniline was first produced in 1826 by dry distillation of indigo. Traditionally, it has been prepared by nitrating benzene, then reducing the nitrobenzene with iron and hydrochloric acid such as in the reduction of nitrobenzene with iron filings or borings and 30 percent hydrochloric acid; catalytic reaction of chlorobenzene with aqueous ammonia in the vapor phase and the reduction of nitrobenzene with hydrogen. Also a catalytic (Al.sub.2 O.sub.3) process is known wherein the organic amines are obtained by ammoniation of phenolic-type compounds; U.S. Pat. No. 3,860,650. Additionally, phenol can also be subjected to gas phase ammonolysis with the Halcon-Scientific Design process. This process employs high temperatures and high pressures and is catalyzed by catalysts such as alumina-silica and mixtures of manganese-boron oxides and alumina-titania or are combined with additional co-catalysts such as cerium, vanadium or tungsten. Although selectivity in such processes is as high as 90 percent, highly undesirable by-products such as diphenylamine and carbazole are produced. U.S. Pat. No. 3,272,865 is drawn to a method of obtaining high yields of aromatic amines from hydroxybenzenes by catalytic exchange of the hydroxyl group for the amino group in the presence of ammonia. It is also of interest in that it uses silica-alumina, titanium-alumina, zirconia-alumina catalysts plus phosphoric acid and tungsten oxide apparently as co-catalysts.